The goal of this proposal is to delineate the role of the small intestine in human zinc (zn) homeostasis, with special reference to post-prandial secretion-reabsorption of endogenous zn. This objective will be achieved by a combination of multi-lumen intestinal intubation/perfusion, stable isotope kinetic and model based compartmental analysis techniques. These techniques will be used for quantitative evaluation of zn homeostasis in the small intestine over a range of dietary zn intakes in normal subjects and in patients with cystic fibrosis (cf).